MOLLUSCA OR UNIVALVES. 255 



largest species, being more than four inches in 

 length. It inhabits the American seas. 



120. Erato (Risso). — Shell, spire conical; 

 apex rather round, blunt ; shell, 

 when young, smooth ; the adult ||||p 

 with both lips finely marked ^jjpi 

 with lines; columella concave, 

 plaited or smooth. A groove down the back 

 of the shell. Animal like that of Cyprcea. 

 From the Pacific Ocean. 



121. Ovula. — Shell oblong; 

 inner lip without teeth; outer 

 slightly toothed or wrinkled, the 

 extremities generally projecting; 

 spire quite hidden. Animal very 

 similar to that of the Cyprcea; 

 the mantle, however, has only 

 one lobe, which folds over the 

 left lip. — 12 species recent, and 2 fossil. 



In some species the ends of the mouth are 

 so much lengthened as to make the shell fusi- 

 form or spindle-shaped. The Ovula oviformis 

 is perfectly white outside, and of an orange 

 brown within ; the young shell is as thin as 

 paper. 



